Naoki Kawashima

Improving Releasability of Mold Materials for IC Encapsulation Using Epoxy Compounds

The effect of dopants such as zirconium and nitrogen on the releasability of Y2O3-based ceramics from molds was investigated for integrated circuit packaging using epoxy molding compounds (EMCs). Co-doping of these elements was carried out by annealing the surfaces of 5mol% ZrO2-Y2O3 samples under a N2 flow at 1100-1300 °C, resulting in concentration of nitrogen near the surfaces of the samples. The adhesion strength was minimized by exposure at about 1200-1250 °C, which was less than half the value for the undoped Y2O3. The co-doping remarkably decreased the polar part of the surface energy and consequently hydrophobicity of the ceramic surfaces increased. The excellent releasability characteristics were likely related to the depression of dissociative adsorption of water molecules, which are considered to act as active sites for the adhesion of EMCs.

Design of Mold Materials with Excellent Releasability for IC Encapsulation using Epoxy Compounds

Adhesion between epoxy molding compounds (EMCs) and encapsulating mold surfaces is becoming a critical issue for integrated circuit (IC) packaging. Such adhesion results in IC damage or a serious reduction in productivity of the packaging process. It is thus highly desirable to develop mold materials that have excellent releasing properties for EMCs. In this study, the adhesion strengths of various oxide ceramics selected as model surfaces for mold materials for conventional EMCs were measured at room temperature. Some rare-earth oxides, which have surface isoelectric points (IEPs) of the oxide of approximately 9, exhibit excellent releasability from EMCs. This is considered to be caused by inhibiting acid-base interactions between EMCs and the oxide surfaces.

Improvement in Oxidation and Thermal Shock Resistance of Molten Glass-Coated Carbon Materials by Interfacial Control

The coating of molten silicate glass on a porous carbon substrate was developed, without the formation of cristobalite at the carbon-glass layer interface, in order to improve the steam oxidation and thermal shock resistance. Initially, suitable conditions for coating were assumed from thermodynamic analysis. Based on these calculations, the wettability of the carbon to molten glass was modified by infiltration and pyrolysis of a Si-N precursor, and the coating with glass was carried out under higher N2 partial pressures. As a result, carbon substrates were completely sealed with glass, without the production of cristobalite at the interface, and the glass was infiltrated into the substrate. In contrast, coating with glass at lower N2 partial pressures, such as in Ar, were followed by the formation of cristobalite along with many pores at the interface. The structural changes occurring as a result of variation of the N2 partial pressure during sealing with glass are in good agreement with the thermodynamic analysis. The glass-coated carbon materials, which were fabricated at higher N2 partial pressure, possessed excellent steam oxidation resistance and thermal shock resistance.